Nuanced question about USB/MIDI Controllers + Arduino/Raspberry Pi

I'm no beginner to software, but when it comes to hardware I am mostly an outsider. I enjoy leveraging Pi 4B for various projects, but I have wanted to take on a larger project more recently. I want to make a USB/MIDI controller of various potentiometers, slide pots, buttons, etc. and connect the controller to a raspberry pi with an LCD screen running software that reads the USB/MIDI arduino controller. My questions are: 1. Can a single Raspberry Pi 4B be capable of running Pi OS on a 7"+ LCD, outputting sound via RCA or 3.5mm output, and simultaneously also read digital/analogue ins from knobs, faders, buttons, and switches and convert them to USB MIDI for software on Pi OS to interpret or would I be better off using an Arduino in addition to the Pi as the usb midi controller handling the inputs 2. How can a Raspberry Pi 4B output sound via stereo RCA and 3.5mm simultaneously? How would I leverage a DAC breakout while still being able to use the 4-pole 3.5mm audio jack already on the pi? 3. In the case that I have both an arduino & raspberru pi 4b, what type of power supply situation would be needed to both power the Pi + LCD and the Arduino? Can I power it from a single power cable? Apologies if a lot of these questions are naive, I am simply interested in taking on a larger hardware project, but most of my tacit knowledge really exists in software so I'm looking for help, thanks! :)

Raspberry Pi OS isn't a real time OS = You can't be 100% sure that you get the resources when its needed. Arduino is a better choice as a MIDI controller.

If I use the Arduono as the USB MIDI controller, how can I power it from the Raspberry Pi so I can use one single power cable, I assume 5V 3A is enough, but how would I power the Arduino and the LCD through the Pi?

On the 40 pin connector is both 5 and 3,3 volt available